Beta tubulin is expressed less intensity in the thoraces (mostly flight muscles) of diapausing than nondiapausing mosquitoes, but the abdomens express beta tubulin at similar levels in both types of mosquitoes. Expression was slightly lower in the heads of nondiapausing mosquitoes. The same patterns were evident in early and mid diapause. Microtubule formation was also lower in the thoraces of diapausing adults, as confirmed by confocal laser microscopy staining with an indirect immunofluorescent method. Midgut microscopy images (abdomens) of early nondiapausing and diapausing mosquitoes were compared using pixel intensity and the results showed no significant difference between them. In contrast, statistical analysis of the thorax images of early nondiapausing and diapausing mosquitoes indicated significantly less staining of the microtubules in the diapausing mosquitoes. Low temperature decreased the microtubule level in midguts of nondiapausing mosquitoes, but the midgut levels of diapausing mosquitoes remained unchanged by low temperature. Midguts exposed to -5°C for 12 hours had similar microtubule currents in nondiapausing and diapausing mosquitoes. Pixel intensity averages were higher in the thoracic muscles than in the midguts, but the thoracic muscles showed similar patterns between diapausing and nondiapausing mosquitoes at low temperatures. The reduced microtubule expression in the flight muscles is likely to be linked to the lower activity of flight muscles during diapause. Nondiapausing mosquitoes showed a dramatically decreased pixel intensity of microtubules in when tissues were exposed to low temperature, but in diapausing mosquitoes low pixel intensity, was observed consistently even in response to cold stress.